“It’s been kind of a picture-perfect year. I wouldn’t necessarily assume any negative impact (from the rain),” he said.

Between 2:30 and 6 p.m. Thursday, 1.82 inches of rain fell at the Salem, Ore., airport, Paul Walker, Accuweather senior meteorologist, said. Other parts of the Willamette Valley received varying amounts of rain and some hail. Walker said the downpour, accompanied by thunder and lightning, was caused by a cool pocket of air moving inland from the Pacific Ocean that trapped warm air underneath and caused the atmosphere to become unstable.

“It’s a little early in the season for that type of storm, but not uncommon,” Walker said. “We’ll probably go back and forth between warm and cold over the next two to three weeks.”

Generally the problem for wine growers is not enough rain — the rain we’ve had has been positive, said Charles Humble, Oregon Wine Board director of communications and interactive marketing.

“We’ve had a great growing season of dry and warm weather,” Humble said. “It’s just a matter of (growers) deciding when they want to pick the grapes.”

As planned, Casteel expects he’ll begin harvesting Bethel Heights Pinot and Chardonnay grapes in less than two weeks.

“The unknown is what the weather is going to be between now and 10 days from now,” Casteel said, adding that 2013 is one of the earliest harvest years he has experienced in 30 years of winemaking.

Denfeld said hazelnuts have been falling for about 10 days and will remain on the ground for the next couple of weeks until growers are ready to begin harvesting. If rain continues, the biggest threat to crops is mold.

“There have been other years where we’ve had some moisture in September and we had a mold problem,” Denfeld said.

When more than 5 percent of a yield is affected by mold, grading for in-shell nuts is compromised, meaning the nuts will have to be cracked and the moldy nuts removed by hand, said Denfeld, whose 300-acre hazelnut orchard is eight miles south of Hillsboro.

Denfeld Orchard also grows 200 acres of walnuts. He said walnuts aren’t expected to be harvested for another two to three weeks and shouldn’t be affected by the recent rains.